Some notes on bulb inclination and on using a general VPP for modelling its effects

The use of fin keels and ballast bulbs on modern high-performance yachts presumably means that the design and performance characteristics of such appendages are more or less well understood, but the question of how much to incline the bulb of a ballast keel seems to have little hard analysis in the open literature. This paper attempts to provide a brief theoretical analysis and derived VPP predictions. There are some practical results from radio-controlled racing yachts. Velocity prediction programs (VPPs) are general-purpose tools that model the major factors affecting a yacht’s performance, and may often not accommodate a particular variable of interest. The paper outlines a simple technique for employing a general-purpose VPP to explore the effect of variables that are considered "not available" in that VPP, illustrated by using the technique to address the problem of the appropriate angle of inclination for a ballast bulb.